The wife of the man who stormed into a one-room Amish schoolhouse in Lancaster County, Pa., seven years ago, shooting 10 schoolgirls, five of them fatally, will never forget the phone call she got from her husband early that morning.

He said she would never see him again, and she pleaded with him to come home and talk to her, even though she had no idea of the horror he was about to unleash.

The crime stunned the nation, not only because of the brutality against young children, but because it took place in traditional Christian community whose residents are known for their peaceable ways and avoidance of the modern world.

The gunman was Charles Roberts, a father of three and husband. Roberts, his wife, Marie, and their children lived one mile away from the school.

His then-wife -- who has since remarried and taken the last name Monville -- is now talking about the tragedy that changed so many lives, including her own.

In an interview with ABC News' Amy Robach, Monville, 35, was asked if she knew why her husband did what he did.

Monville described Roberts as an even-tempered man who had periodic, brief bouts of depression. She said they'd grown a bit distant from each other in their marriage, but had no inkling that her 32-year-old husband could commit such an act.

On the morning of Oct. 2, 2006, Roberts, a milk truck driver, saw his children off to the school bus and kissed his wife goodbye before leaving the house, but three hours later, he called to tell Marie that he was never coming home, and that he'd left her a letter. His voice sounded "flat and lifeless."

She immediately became alarmed, and pleaded with him to reconsider what he was about to do. Monville told Robach she thought he was going to commit suicide.

'It Was Too Late'

"I just thought it was something that he was doing to himself," she said. "I had no idea that it was going to involve other people. And he didn't allude to that on the phone in any way."

She recalled that she was "begging him" to come home and talk, but "he was telling me that it was too late."

In his letter to her, her husband wrote about the loss of their first daughter, Elise, in 1997, Monville said. Elise, the couple's first child, died 20 minutes after being born three months premature.

"And in some way he felt like he was getting back at the Lord for the loss that we had sustained," she said.

He also told her that he'd molested two family members decades ago, but Monville said police investigated that claim and could not prove it.

When she read the letter, she called 911 because she felt something bad was going to happen to her husband.

That morning, she heard sirens blaring. Police cars were passing by, and helicopters were flying overhead. When police knocked on her door, her dread intensified.

"When I opened the door I said to them 'It's Charlie, isn't it?' And they said 'yes.' And I said, 'and he's dead, isn't he?' And they said 'yes,'" she said.

When she learned that he hadn't just killed himself, but had shot little girls, she cried. Police were positive her husband was responsible, and she believed them.

"There were so many things to do, and so many questions to answer," she said.

Roberts had reportedly ordered the male teacher and male students out of the schoolroom at West Nickel Mines Amish School, along with a pregnant woman and parents with young children. Police say he barricaded himself in the room with the female students, lined them up against the blackboard, and shot them.

In an apparent effort to buy time for her classmates, Marian Fisher, 13, the oldest of the five girls who were killed, reportedly asked Roberts to shoot her first.

Mentally Ill?

Asked if she believed her husband was mentally ill, she replied: "On that day, he was absolutely mentally ill. I don't see how someone could so something like that and not be."

In the years since the shooting, Monville has spent time with counselors, trying to understand how the shooting could have happened.

"It was suggested to me that all those years of undealt-with depression resulted in a psychotic break," she said. "And I think we all want answers. And while that ... is, to some degree, an answer, it's still not an answer. Because all the times that I said, 'Why don't you talk about this with someone? Can you talk about it with me? Can you talk about it with your parents? Could you talk about it with someone at church? Don't you have a friend you could talk about this with?' And I was always met with the same resistance and the same 'No, I can handle this on my own.' It was obvious at the end, that he couldn't."

Monville writes about her life with Roberts and what has happened since then in her book, "One Light Still Shines." In it, she credits God with helping her get through the terrible moments since then.

Monville told Robach about having to break the news of their father's death -- and crimes -- to her children. Abigail was 7, Bryce was 5 and Carson was 18 months old.

Their children had been so sheltered that they never even saw the news at home, Monville said.

"You know, I wanted to protect them from the evil of this world. And suddenly evil had invaded our home. And there wasn't any way to protect from that," she said.

She added: "You know, we talked a lot about the choice that Charlie made, and how it wasn't a reflection on them. And it wasn't their fault. There wasn't anything they could have done differently that would have stopped them."

Even as she was struggling to come to grips with her husband's death and his crimes, outreach from the Amish community was on its way.

Victims' Community Forgives

Hours after learning about what Charles Roberts had done, a contingent of the grieving Amish came to visit her.

Monville recalled that she was standing in her parents' kitchen, and she could see a group of the Amish walking towards her parents' home.

Her father offered to go outside and talk to them.

"And I couldn't hear the words they were saying, but I could see the exchange that was happening. I could see their arms extending. And the way they laid their hands on my dad's shoulder. I could feel it," she said.

"I could feel the emotion of the moment. You know, it said everything," she said, adding that her father said they had forgiven her husband. "They were concerned about me and concerned about the kids, and wanted us to know that they supported our family."

It didn't end there. When her family was besieged by media en route to bury Charles Roberts, the Amish stepped in again. Even though they don't like to have their pictures taken, members of the community placed themselves directly in front of news cameras to shield her family, Monville said.

"They turned their backs to the cameras so the only pictures that could be taken were of them and not of our family. And it was amazing to me that they would choose to do that for us," she said. "It was amazing. It was one of those moments during the week where my breath was taken away, but not because of the evil. But because of the love."

It wasn't long after her husband's death that she found love again. Dan Monville, 47, an insurance agent, who was a member of local church network, reached out to offer Marie support. Their relationship flourished, and they were married in May 2007.

Even though she was initially resistant to even contemplating thoughts about marriage so soon after the tragedy, she said: "I really felt the Lord speak to me that Dan was the man I was going to marry."

She knew some people would think it was too soon, but she trusted that God was leading her, she said.

"As radical as it sounded to trust the Lord in the potential of marrying someone so soon after, I had come from this place of desperation and saw God walking me through it and working out places of beauty from the ashes of my life," she said.

Marie Monville says she has forgiven Charles Roberts, even though it wasn't easy.

"Charlie had an illness. And it doesn't excuse what he did ... But, you know, if I allow bitterness and anger to live inside of me? Those were the very things that pushed him to do what he did. I don't want anything to do with that," she said.

"It's not like I could forgive him once for what he did and never have to think about it again. It's something that I think about all the time," she said. "But I don't have to just forgive Charlie for him. I have to forgive him so that I can be whole, and so that it doesn't eat away inside of me the same way that he allowed anger to eat away inside of him."